If they have any covid symptoms, they should immediately get tested (and PCR test is the gold standard). If positive, they should call their primary care doctor immediately and tell them they have symptoms and make sure the doctor understands their health issues. In Minnesota (and I imagine elsewhere), the distribution of these FDA emergency approved medicines is controlled by the State, there are not enough drugs to go around, and they are distributed on a point system based on health conditions. And with my experience, realize this virus is far more contagious than people realize, take extra care including packaging and indoor spaces. Also check with doctor to see if they are eligible for the 4th dose(second booster)